This "checking out the girl" only took a few minutes, some time before the chuppa, and there was probably no yechud, because if there was real yechud why is this any different than Yehuda (Or parts of Yehuda) where they were meyached the choson and kallah between the ayrusin and nesuin (Rashi, Ksuvos 9b). Or more specifically by the ayrusin party (Rav Ovadia, Ksuvos P1, M5).
And even though in Yevamos P4, M10 Rav Ovadia says like the Brysa (Ksuvos 12a) that the yechud was done before the chuppa, we must say that "one hour before the chuppa" means "one hour, anytime before the chuppa", even by the ayrusin party.
Notice that it doesn't say "one hour before the actual chuppa". It says "one hour before they went into the chuppa, which can also mean "one hour anytime before the chuppa." And anyway, if it literally meant one hour before the chuppa, what does this have to do with eating by the in-laws from ayrusin till nesuin? Even if he never ate by the in-laws he can still do yechud in the wedding hall before the wedding, so why are we talking about the in-laws?
So you must say that this yechud business could have happened anytime between ayrusin and nisuin, and that's why they had to say sheva brachos by the ayrusin (Rashi and Tosfos, Ksuvos 7b) because it's forbidden to live with your kallah without sheva brachos.
The bottom line is that all this had nothing to do with "checking her out" before the chuppa, where he can still have taynis besulim because there wasn't much yechud.